1. Field of the Invention
The present invention relates to a metal core substrate and a manufacturing process thereof.
2. Description of the Related Art
A metal core substrate is known and is used as a package on which a semiconductor chip is mounted.
Concerning the metal core substrate, there have been provided various types of structure. According to the official gazette of Japanese Unexamined Patent Publication (Kokai) No. 2000-244130, there is disclosed a metal core substrate which has a coaxial structure, of a so-called xe2x80x9cVia in Viaxe2x80x9d type, which reduces inductance and also has a capacitor structure inside.
As shown in FIG. 18, this metal core substrate 1 is composed as follows. On the metal plate 2, through-holes 3 are formed, and the upper and lower wiring patterns 5 are electrically connected with each other by the through-hole plating films 4 in a structure called xe2x80x9cVia in Viaxe2x80x9d. On both sides of the metal plate 2, the copper foil layers 7, 7 are provided via the dielectric layers 6. These copper foil layers 7, 7 are electrically connected to the through-hole plating films 4. On the other hand, the other through-hole plating film 8 and the metal plate 2 are electrically connected with each other, so that capacitor structures are formed between the metal plate 2 and the copper foil layers 7, 7, respectively.
The above metal core substrate 1 provides an effect that the inductance can be reduced. Further, the above metal core substrate 1 provides an effect of effectively removing noise because the capacitor structure is formed at a position right below the semiconductor chip which is to be mounted.
However, as shown in FIG. 18, both the through-hole for signal use and the through-hole used for connection of the metal plate 2 exist on the above metal core substrate 1. Therefore, the density of the wiring pattern for signal use must be restricted, that is, it does not allow an increase in the density.
The present invention has been accomplished to solve the above problems.
It is an object of the present invention to provide a metal core substrate, and a manufacturing method thereof, characterized in that the electric performance can be enhanced and high density wiring can be provided.
According to the present invention, there is provided a metal core substrate comprising: a core layer comprising first and second metal plates layered by means of a third insulating layer interposed therebetween; first and second insulating layers formed on the first and second metal plates, respectively; first and second wiring patterns formed on the first and second insulating layers, respectively; a conductive means formed in a through-hole penetrating the first insulating layer, the first metal plate, the third insulating layer, the second metal plate and the second insulating layer to be exposed to insulating portions with respect to the first and second metal plates, respectively, for electrically connecting the first wiring pattern with the second wiring pattern; first connecting means for electrically connecting the first metal plate with the first wiring pattern and the second wiring pattern, respectively, by means of a via penetrating the first insulating layer and by means a via formed in a via-hole penetrating the second insulating layer, the second metal plate and the third insulating layer so as to be exposed to an insulating portion with respect to the second metal plate; and second connecting means for electrically connecting the second metal plate with the second wiring pattern and the first wiring pattern, respectively, by means of a via penetrating the second insulating layer and by means a via formed in a via-hole penetrating the first insulating layer, the first metal plate and the third insulating layer so as to be exposed to an insulating portion with respect to the first metal plate.
The first metal plate is a ground plane and the second metal plate is a power plane.
The first and second wiring patterns are multi-layered patterns formed in and on the first and second insulating layers, respectively.
The third insulating layer may preferably be a dielectric layer.
According to another aspect of the present invention, there is provided a metal core substrate comprising a core layer comprising first and second metal plates layered with a third insulating layer interposed therebetween, the first and second metal plates having first through-holes at positions overlapping to each other in a core thickness direction, the first and second metal plates also having third and fourth through-holes, respectively, at positions not overlapping to each other in the core thickness direction; first and second insulating layers formed on the first and second metal plates, respectively, so that the first, third and fourth through-holes are embedded therewith; the first, second and third insulating layers having a second through-hole penetrating therethrough and penetrating the first through-holes so as not to be exposed to the first and second metal plates, respectively; the first and third insulating layers having a first via-hole penetrating therethrough and penetrating the third through-hole to be exposed to the second metal plate, but not to be exposed to the first metal plate; the second insulating layer having a second via-hole penetrating therethrough to be exposed to the second metal plate; the second and third insulating layers having a third via-hole penetrating therethrough and penetrating the fourth through-hole to be exposed to the first metal plate, but not to be exposed to the second metal plate; the first insulating layer having a fourth via-hole penetrating therethrough to be exposed to the first metal plate; first and second wiring patterns formed on the first and second insulating layers, respectively; a conductive means formed in the second through-hole for electrically connecting the first wiring pattern with the second wiring pattern; a first via formed in the first via-hole for electrically connecting the second metal plate with the first wiring pattern; a second via formed in the second via-hole for electrically connecting the second metal plate with the second wiring pattern; a third via formed in the third via-hole for electrically connecting the first metal plate with the second wiring pattern; and a fourth via formed in the fourth via-hole for electrically connecting the first metal plate with the first wiring pattern.
The second through-hole has a diameter smaller than that of the first through-holes, the first via-hole has a diameter smaller than that of the third through-hole, and the third via-hole has a diameter smaller than that of the fourth through-hole.
The first through-hole of the first metal layer and the third through-hole of the first metal layer are coaxially formed as a single through-hole which has a diameter (A) larger than that (B) of the first through-hole of the second metal layer; the second through-hole and the first via-hole are coaxially formed in such a manner that a diameter (C) of the first via-hole is smaller than that (A) of the third through-hole and larger than that (B) of first through-hole, and a diameter (D) of the second through-hole is smaller than that (B) of the first through-hole; and the first via and conductive means are coaxial in such a manner that an insulating portion is interposed therebetween.
According to still another aspect of the present invention, there is provided a process for manufacturing a metal core substrate comprising the following steps of: preparing a core layer comprising first and second metal plates layered with a third insulating layer interposed therebetween; forming the first and second metal plates with first through-holes, respectively, at positions overlapping to each other in a core thickness direction and with third and fourth through-holes, respectively, at positions not overlapping each other in the core thickness direction; laminating first and second insulating layers on the first and metal plates, respectively, so that the first, third and fourth through-holes are embedded therewith; forming the first, second and third insulating layers with a second through-hole penetrating therethrough and penetrating the first through-holes so as not to be exposed to the first and second metal plates, respectively; the first and third insulating layers with a first via-hole penetrating therethrough and penetrating the third through-hole to be exposed to the second metal plate, but not to be exposed to the first metal plate; the second insulating layer with a second via-hole penetrating therethrough to be exposed to the second metal plate; the second and third insulating layers with a third via-hole penetrating therethrough and penetrating the fourth through-hole to be exposed to the first metal plate, but not to be exposed to the first metal plate; and the first insulating layer with a fourth via-hole penetrating therethrough to be exposed to the first metal plate; forming a conductive means in the second through-hole, a first via in the first via-hole, a second via in the second via-hole, a third via formed in the third via-hole, and a fourth via formed in the fourth via-hole; forming first and second wiring patterns formed on the first and second insulating layers, respectively, so as to be electrically connected to the conductive means, the first via, the second via, the third via, and the fourth via.